Blasting cap



Sept. l, 1931. H. Kl 'BABBlT-r 1,821,608

lBLASTING CAP Filed June l, 1929 Bq his aHorneLl Patented Sept. l, 193iHENRY K. BABBITT, OF WILMINGTON,

ISTATES PATENT FFICE DELAWARE, ASSIGNOR T0 E. I. DU PON'Jl' DE tantosNEMOURS & COMPANY, 0F WILMINGTON, DELAWARE, A CORPORATION 0F DEL- AWAREIBLASTING CAI Application led June 1, 1929. Serial No. 367,805.

This invention relates to delay electric.

blasting caps, and more particularly to means for releasing the pressureof the gaseous products of combustion of the priming charge in order toprevent pre-ignition of the explosive charge.

Delay action caps for use in mining and blasting operations haveheretofore comprised essentially a shell containing a suitable explosivesubstance, such as fulminate of mercury, or tetryl at its inner end, aplug of sulphur or like substance at the outer end, through whichinsulated conducting wires for the shot firing circuit pass to theigniting compound, and a retarding means containing a core or train ofslow burning powder interposed between and spacing the A fuse end of thecartridge and the detonating end.

Various methods have been suggested for the escape of the gases andavoidance of pressure within the shell, such as providing vent holes inthe shell wall, and it has been proposed to carry a rubber jacket overthe perforations' for the purpose of excluding moisture. Closable ventslaterally to the fuse which open automatically under the action of thegenerated pressure have been suggested by Eschbach (UQS. Patent N o.1,57 0,- 733). Eschbach furthermore provides a free-air space betweenthe fuse cartridge and the retarding means and an air ventconimunicating with the space within the fuse for the escape of thegases and pressure resulting from the ignition of the match head inorder to prevent-pre-ignition of the shot.

An object of the present invention is to provide a means whereby theheated gases and pressure produced within the cartridge at the time ofinitial ignition may be allowed to escape at as low a temperature aspossible so as to avoid premature ignition of the explosive material inwhich the blasting cap is embedded or surrounded.

Another object of mv invention is a means whereby the gas is diffused inorder to provide greater cooling effect of the gases than has heretoforebeen the practice.

A further object lof this invention is a device having the foregoing andother advantages and at the same time may be more simply constructedthan devices of the prior art.

Other objects tion proceeds.

These objects may, be accomplished by means of an outer sleeve adaptedto fit over the electric detonator and engage the casing at a pointbelow the ventvin the wall.` This sleeve should be slightly larger thanthe shell of the fuse cartridge and spaced therefrom to permit readyexit of the gases. For this purpose spacing means inside the sleeve areessential, andin my preferred form I propose to provide an inner beadwhich, besides serving as a spacing means between the sleeve and theshell of the fuse will appear as the descrip-v cartridge, will also forma spiral channel v through which the escaping gases may pass. In thismanner the desired cooling effect may be produced due to the extremelength of the channel and the diffusion of the gases that occurs. Wherethe spiral bead is not desired, pointed or oblong beads may be provided.I

My invention is illustrated by way of ex* ample in the accompanyingdrawings in which:

Figure 1 is a view of one4 form of my proy .ings it will be seen that 1represents the in-v sulated conducting wiresof the shot firing circuit,2 the sleeve member, 3 the ignition head, 4 spacing means for thesleevev member, 5 the spiral bead forming a channel for the escape ofthe gaseous products of combustion, 6 the gas vent, communicating withthe free air space within the electric detonator, 7 the cap load, 8 and9 sulphur plugs, 10 the'waterproofing compound, 11

the ignition (match) in place. In Figure 3 1s fled form ofthe sleeveWithout the spiral bead,

this form being a plain sleeve vwhich fits over the detonator and isspaced therefrom by means of the pointed bead shown at 4b. This beadmay, of course, lbe provided on either the sleeve or the shell of thedetonator as desired as it will serve the same function equally wellsince it acts merely as a spacing means. This bead may also take anoblong form such as that shown at 4a in Figure 4;, in which case it maylikewise be produced on the lshell of the detonator; v y

It will be understood that the foregoing parts are those conventionallyused in this type of detonator. My improvement conslists principally inproviding the sleeve W ich may be inserted over the detonator andadapted to engage the shell of thesame below the exit vent for thegases. f

rlhe sleeve may becombined with the detonator in various ways.Preferably, l pose to crimp thelower end of the sleeve so as to engagethe grooves inthe retarding element, together with the shell of theblasting cap. The retarding agent may consist ofl any one of severalmaterials such as black powder, fuse, or other slow burning materials. ylln somel cases it will be found desirableto have the gas vent closed atthe exit from the air chamber, and for this purpose l propose to providea low melting wax, lacquer or pyroxylin covering for the vent to preventundue moisture or water from entering the air chamber., Other suitablemeans for closing the vent may be used, such as low melting solder, -butl prefer to use a pyroxylin material because of its quick responsetoincrease in temperature.

vAs many changes may be made in the above construction, and asapparently many Widely .dierent embodiments o'f my invention may be madewithout departi from the spirit or scope thereof, it is inten edthat allmatter contained in the .accompanying specification 'and drawings shallbe interpreted as illustrative merely, and that my invention shall notbe limited exceptas stateduin the following claims.:

l claim: v

Y 14. Al delay el tric'detonator comprising in combination an ignitionhead,3an explosive load, a retardingmeans interposed between theignition head and theload means, a free air-space between the ignitionhead and the retarding means, a vent .in vcommunication -with `the freeair space fox-,exit of the gases formed during initial firing, a fillerof lo'w fllsiblev Ar'naterial covering the vent,-l andy a sleevesurrounding the detonatorand spaced therefrom, and provided with aninnerspiral air-space between retardmg means, a vent 1n communication withthe free air-space for exit of the' gases vformed during initial firing,fusible materialicovering the vent, a sleeve surrounding the detonator,said sleeve having a spiral rib adapted to space the sleeve from theydetonator and form a spiral channel for thedifusion and exit of thegases of combustion formed during initial ring so as to a illerof lowprevent pre-ignition of the detonator charge'.

In testimony whereof, I aflx my signature.

v HENRY K. BABBITT.

